In a typical flexible medium disk drive system, the flexible medium of the disk has signals magnetically encoded on the flexible medium. The disk rotates and a disk drive sensor senses the magnetic signals as the flexible medium rotates past the disk drive sensor. The disk drive sensor converts the magnetic signals to electrical signals for use by other systems.
The magnetic signal levels of the disk decrease substantially exponentially with the distance from the flexible medium of the disk. Therefore, it is desired to place the disk drive sensor as close as possible to the flexible medium. Additionally, the speed of current disk drives causes the flexible medium to vibrate out-of-plane, which in turn, may decrease the accuracy of the communication between the flexible medium and the disk drive. Therefore, it is desired to reduce vibration of the flexible medium in the region near the disk drive sensor.
A typical disk drive system includes a head head stack assembly including two head gimbal assemblies positioned such that their heads face each other and are placed on opposite sides of the flexible medium. The heads include sensors for sensing the magnetic signals of the flexible medium. A force is applied to the two heads, sandwiching the flexible medium between the two heads. The sandwiching of the flexible medium between the two heads decreases the out-of-plane vibration of the flexible medium in the region of the heads, resulting in increased accuracy of communication between the flexible medium and the disk drive. Generally, increasing the force will reduce the out-of-plane vibration of the flexible medium and increase the accuracy of the communication.
However, increasing the force too much may adversely affect the system by increasing the wear of the flexible medium and/or the heads. To further explain, a rotating disk in conjunction with the heads creates an area of increased air pressure near the surface of the disk and beneath the heads that pushes the head gimbal assembly slightly away from the surface of the flexible medium. This phenomena causes portions of the heads to “fly” slightly above the surface of the flexible medium.
Because portions of the heads are “flying” above the surface of the flexible medium, the head gimbal assembly does not significantly wear the flexible medium. However, because portions of the heads are flying above the surface of the flexible medium, the flexible medium is allowed to vibrate, albeit less than if the flexible medium were not sandwiched between the two heads of the head stack assembly.
Therefore, if the forces pushing the heads of the head stack assembly together are increased significantly, the disk drive heads may rub against the flexible medium with a relatively large force, which in turn may increase the wear of the flexible medium and/or the head. Thus, simply increasing the forces pushing the heads together is of limited value in further reducing out-of-plane vibration of the flexible medium. Conventional techniques disclose keeping the disk drive heads as parallel as possible to the flexible medium and selecting a force that minimizes both vibration and wear.
In view of the above problems, there is a recognized need for a system and method of reducing flexible medium out-of-plane vibration to increase the accuracy and speed of a disk drive. The present invention satisfies this need.